Question

A radioactive nucleus decays as follows: \[ X \xrightarrow{\alpha} X_1 \xrightarrow{\beta^-} X_2 \xrightarrow{\alpha} X_3 \xrightarrow{\gamma} X_4 \] If the mass number and atomic number of \( X_4 \) are 172 and 69 respectively, then the atomic number and mass number of \( X \) are

• A. 72, 180
• B. 69, 170
• C. 68, 172
• D. 70, 172

Hint:

Decay problems: \begin{itemize} \item Work backward carefully. \item Track A and Z separately. \end{itemize}

Answer 1

The Correct Option is A